The invention generally relates to implantable devices, specifically relating to devices for the prevention of unwanted scar tissue. The invention more particularly concerns a multi-layered device which serves to prevent unwanted adhesion formation following a surgical procedure.
Adhesions following surgery are a common result of the body's natural healing process. Unfortunately, nearly all surgeries have the risk of unwanted adhesions. Some adhesions cause or can lead to significant morbidity or mortality for the patient. For example, adhesions which follow abdominal or pelvic surgery may lead to bowel obstruction for the patient within months or even up to years subsequent to the original surgery. Many adhesions increase the risk and difficulty of second operations. Repeat cesarean sections are much more difficult and can risk injuring the uterus or bladder if significant post-operative adhesions are present. Adhesions following cardiac surgery also greatly increase the risk of a second operation. Approximately fifteen percent of cardiac surgery are “redo” or repeated surgeries. In these “redo” cases, the heart, bypass grafts or great vessels can be injured during the repeat sternotomy due to adhesions holding these structures against or near the sternum. In these cases, significant pre-sternotomy preparation must be performed, such as preparation of the groin for possible cannulation and peripheral cardiopulmonary bypass in the event that the heart or a great vessel is injured during the sternotomy. Additionally the presence of adhesions adds a tremendous amount of time and difficulty to any surgery. Overall, adhesions increase the risk and cost of any repeat surgery.
It is believed that the inflammatory process which results in adhesions occurs in the first few days following an operation or procedure. The single concept to date in anti-adhesion barrier technology has been a biomaterial which separates tissues and prevents the adhesion of tissues to the biomaterial or to one anther. Currently available single layered anti-adhesion barriers have only had some success at preventing these post-operative adhesions. Adhesions do occur in the area where the resorbable barriers were placed. In the design of these single layered barriers, the thought is that they will physically separate the tissues for longer than the first few post-operative days and then be resorbed. Additionally these barriers are composed of material believed to be anti-adhesive in nature. These single layered or functionally single layered (multiple layers which do not separate or have designated middle layers to provide physical separation between outer layers) may fail to completely prevent adhesions because the opposing tissue actually forms one or more adhesions to the barrier material. When the barrier material is resorbed, if adhesions have formed on opposite sides of the material, those tissues will then likely remain bonded to each other as the resorbable material between them degrades. In summary, single layered or functionally single layered barriers are inadequate to prevent adhesions possibly due to the incomplete anti-adhesive quality of their materials and the limitation of their design in that their success is based on the anti-adhesive quality of their materials. There have been a number of materials and forms of materials with this approach.
U.S. Pat. No. 6,030,958 (Burns et al.) describes a film constructed from a polyanionic polysaccharide which is placed between tissues and remains there long enough to prevent the tissues from healing together. The film then disperses and is completely resorbed into the body.
U.S. Pat. No. 6,548,081 (Sadozai et al.) describes an anti-adhesion composite constructed from hyaluronic acid and a carboiimide. This composite can be a sustained release source of hyaluronic acid to prevent adjacent tissue adhesion.
U.S. Pat. No. 6,391,939 (Wells et al.) describes a construct for the prevention of adhesions derived from collagen. In one embodiment, the collagen is combined with polyethylene glycol to form a construct which will be resorbed in less than one week.
U.S. Pat. No. 6,500,777 (Wiseman et al.) describes a construct for the prevention of adhesions which is a continuous film of oxidized cellulose. The construct is formed in a multi-layer sandwich of cellulose film on the outside and a middle layer such as rayon or a fabric to provide mechanical strength. The cellulose film is non-porous to prevent adherence of cells and molecules to the cellulose film. The middle layer of the construct adds enough strength so it can be sutured. The cellulose film can also be used without the middle layer.
U.S. Pat. No. 5,795,584 (Totakura et al.) describes a surgical adhesion barrier constructed of at least one bioabsorbable polymer. This barrier may be formed from one or more layers of polymers. The polymers may be a combination of resorbable and non-resorbable polymers. The barrier may also contain a medicinal agent between the layers.
U.S. Pat. No. 6,074,663 (Delmotte et al.) describes a bio-mechanical barrier for the prevention of post-operative adhesions formed from cross-linked fibrin. The fibrin film may be multi-layered and may have very small pores to prevent the formation of adhesions to the film.
U.S. Pat. No. 5,356,429 (Seare) describes an elastomeric barrier material that may serve to prevent the re-adherence together of body pocket walls around an implantable prosthesis. Seare describes a dual layer material, with the two outwardly facing opposite sides being textured to encourage cell growth, and the two inside facing surfaces being smooth and non-textured to readily slide with respect to one another. In this embodiment, the two textured sides would adhere to the corresponding tissue surfaces, while the two smooth sides would remain slidable relative to each other, thereby preventing the re-adherence of tissue surfaces.
In summary, the current anti-adhesion technologies strive for a barrier material which will physically separate the tissues without migration, prevent the adhesion of tissue to the barrier, and be resorbed within a few weeks after the adjacent tissues have reduced their propensity to adhere to one another. The delivery of medicinal agents by these barrier materials has also been proposed.
Unfortunately, these anti-adhesion technologies only prevent formation of the adhesions in fifty percent or less of the surgical cases. What is needed is a technology which will overcome the limitations of current anti-adhesion devices allowing the body to form post-operative adhesions in a defined manner and positioning the anti-adhesion construct so the desired surgical and anatomical planes remained preserved.